Alice was the daughter of Arnulph de Montgomery. Arnulph was the fourth son of Roger de Montgomery, who led the center of the Norman army at the Battle of Hastings.

Roger took his name from the castle Sainte Foi de Montgomery in the diocese of Lisieux in Normandy. (Another branch of the Montgomery family took its name from Saint Germain de Montgomery in Calvados).40 The legendary progenitor of the Montgomery family was named Gomer:

"who brought his legions from the war,

and settled the same

Upon a hill 'twixt Rome and Spain,

Gomericus by name;

From which he and his offspring do

Their sir-name still retain."

Roger was made an Earl with large holdings of land in Wales. His family gave its name to the county of Montgomeryshire.

In A.D. 1102, Robert de Belesme, a son of Roger de Montgomery, rebelled against Henry I and was banished from England.40 The Earls of Eglinton descended from other sons of Roger de Montgomery.40

The family of Montgomery in Scotland was founded by Robert de Montgomery in the second part of the 12th century when he obtained the lands of Eaglesham in Renfrewshire.40 The family is that of the Earls of Eglinton and Winton.40

The first Earl of Shrewsbury was named Robert de Montgomery. He was alive before A.D. 1123.40

Alice de Montgomery married Maurice fitzGerald (d. 1176). They had six sons:

William, Baron of Naas.

Gerald, 1st Baron Offaly.

Thomas, Lord of Connello.

Maurice, of Kiltrany.

Alexander.

Robert

The mother of Alice de Montgomery was Lafeacott O'Brien. The O'Brien and the MacCarthy families had been warring with each other in southwestern Ireland for many years prior to the Norman invasion of Ireland. Lafeacott was apparently a persuasive woman. When her son-in-law, Maurice fitzGerald, invaded Ireland in 1171, he took by conquest part of the MacCarthy territory. Initially at least, Maurice did not seize any O'Brien territory of which I have any record.

Most people named O'Brien are descended from Brian mac Cennéidigh, the Ard-Righ (High King) of Ireland usually known as Brian Bóru. Since Lafeacott O'Brien was born only about 150 years after the army of Brian Bóru defeated the Vikings at Clontarf in A.D. 1014, she was undoubtedly aware of her famous ancestor and careful about the spelling of her name. In later generations, the families of (O) Byrne, O'Broin, and Bryan sometimes changed the spelling of their name to O'Brien.84

The father of Alice de Montgomery was probably the same Arnulph de Montgomery who, circa A.D. 1100, founded the Benedictine priory in Monkton known as Pembroke priory, a cell of Seez.